The invention relates to a device for clamping a loaded rod by at least one clamping element acting on the periphery of the rod, wherein the clamping element is conically shaped on its outer periphery and movable in a corresponding conically shaped outer ring, such that the clamping element, when carried by the rod, is pressed against the rod in a self-reinforcing manner in the direction of the load.
Clamping devices of this type are used, for example, to lock in position lifting tables, support cylinders, theater podiums, and the like. Often, they also function as security against falling for vertical axes of machine tools or handling equipment.
Usually, the clamping devices are hydraulically or pneumatically held in the open position and become active with a decrease in pressure. In this case, the energy of the declining load is used to produce the clamping force.
A device for clamping a loaded rod is known from DE 38 11 225, having at least one clamping element acting on a periphery of the rod, the clamping element being conically shaped on its outer periphery and movably mounted in a corresponding conically shaped outer ring, such that the clamping element, when carried by the rod, is pressed in a self-reinforcing manner against the rod in the load direction. In this case, the clamping elements are carried by the rod in the direction of load when they are released, whereby the conical outer contour of the clamping elements produces a self-reinforcing static friction on the rod. The clamping elements do not run against a stop firmly attached to the housing, as long as the nominal load is not substantially exceeded. Therefore, overloads can lead to breakdown of the clamping device due to plastic deformation. This property limits the possible uses to those cases in which overloads are ruled out. For this reason, this clamping device is especially not suited to dissipate the kinetic energy of a falling mass; it blocks the clamping rod, but is not suitable for braking it.
It would be theoretically conceivable to manufacture the parts, such that a stop for the axial displacement of the clamping element is placed in just such a way that a certain clamping force is produced, above which slipping occurs. The aforementioned disadvantage would thus be avoided. However, this cannot be assured with attainable tolerance requirements in practice.